Carbanions electron-transfer equilibria

The red solution of polystyryl carbanions can be kept for days without change in color or viscosity. No changes are observed on addition of further amounts of naphthalene to the red solution. These observations raise some questions. An electron transfer, say for example, between naphthalene" and phenathrene, is a reversible process and it leads eventually to an equilibrium between naphthalene , naphthalene, phenathrene-, and phenanthrene. Is the reaction involving styrene irreversible Now, the initial process of electron transfer from naphthalene to styrene that produces... 

The more acidic fluorene in tert-butyl alcohol solution, or in DMSO solution, reacts by a process that involves the carbanion in equilibrium with hydrocarbon. Thus, fluorene and 9,9-dideuteriofluorene oxidize at identical rates. We have established that the oxidation of the anion of fluorene can be catalyzed by a variety of electron acceptors (v), including various nitroaromatics (18). The catalyzed oxidation rates were found to follow the rates of electron transfer measured by ESR spectroscopy in the absence of oxygen. These results established the catalyzed reaction as a free radical chain process without shedding light upon the mechanism of the uncatalyzed reaction. 

Two kinetic studies of electron-transfer from carbanions to aromatic acceptors will be discussed. The reversible interaction of anthracene, An, with the dimeric-dianions of 1,1-diphenyl ethylene, Na+, DD, Na+, leads to an equilibrium mixture1035,... 

Inactivation is accompanied by the formation of cob(III)aIamin and 5 -deoxyadenosine. (4) The inactivation rate is the same under anaerobic as under aerobic conditions. (5) Substrates are not consumed in suicide inactivation. (6) Inactivation in H20 leads to tritiated substrate and product, but not to tritiated 5 -deoxyadenosine. These facts are accounted for by the mechanism outiined in Figure 22. Catalytic intermediates 2 and 3 in Figure 20 occasionally undergo electron transfer from cob(II)alamin to a free radical center in either 2 or 3, which becomes carbanionic and is immediately quenched by a proton donor in equilibrium... 

An equimolecular mixture of the dicarbanion PTBT " with the diradical PTBT undergoes at room temperature a rapid electron transfer leading to an equilibrium mixture, the major component of which is the radical-carbanion PTBT . This equilibrium can also be attained by controlled oxidation of the dicarbanion PTBT with iodine (Ballester and Pascual,... 

An equilibrium mixture was obtained containing the species MH, MH2, and M . Attempts to prepare stable carbanions of pyrene, perylene and phenanthrene did not succeed. Thermodynamic considerations make it apparent that the carbanions of these ions are very unstable and that the disproportionation reaction (10) is followed by electron transfer processes. 

The reaction involves the transfer of an electron from the alkali metal to naphthalene. The radical nature of the anion-radical has been established from electron spin resonance spectroscopy and the carbanion nature by their reaction with carbon dioxide to form the carboxylic acid derivative. The equilibrium in Eq. 5-65 depends on the electron affinity of the hydrocarbon and the donor properties of the solvent. Biphenyl is less useful than naphthalene since its equilibrium is far less toward the anion-radical than for naphthalene. Anthracene is also less useful even though it easily forms the anion-radical. The anthracene anion-radical is too stable to initiate polymerization. Polar solvents are needed to stabilize the anion-radical, primarily via solvation of the cation. Sodium naphthalene is formed quantitatively in tetrahy-drofuran (THF), but dilution with hydrocarbons results in precipitation of sodium and regeneration of naphthalene. For the less electropositive alkaline-earth metals, an even more polar solent than THF [e.g., hexamethylphosphoramide (HMPA)] is needed. 

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